The third world of the afterlife is supposed to be for people who died by sorcery. Have very many people actually died that way?

Is it only possible for certain personality types to die that way? A warrior personality would naturally choose to die by the sword. A farmer would want to die of old age or something gentler. Who chooses death by sorcery?

Is it perhaps a euphemism for someone choosing to end their own life, or giving into despair? Or dying by bad luck, like in a car accident (which might in older times be attributed to the workings of a sorcerer?)

Recall that no afterlife world is a bad world--simply the company is different in each of the three. Warriors will be your comrades in Valhalla; congressmen and car salesmen will be your comrades in Hela's kingdom.

Maleficium is a Latin term meaning "wrongdoing" or "mischief" and is used to describe malevolent, dangerous, or harmful magic, "evildoing," or "malevolent sorcery." In general, the term applies to any magical act intended to cause harm or death to people or property. Maleficium can involve the act of poisoning or drugging someone with Pharmakeia

I would agroo with the definition found immediately above; I might also suggest that few men have ever possessed adequate command of sorcery to slay another; perhaps the majority of those who died by sorcery, somehow angered one of the many powerful beings who possess far greater magical prowess. It could also be accidental death by sorcery, brought on by the folly of a man reaching past his knowledge and limits. There are many possibilities in the literal sense.

It could also just be any death with no discernable means, thus being attributed to sorcery? That seems less literal and thus less likely, as it seems unlike a being with domain over the dead would confuse death by sorcery with death by something mortals don't know about. I ramble. That is all.

I will just add this: There is a lot to reality we cannot see nor hear. Visible light is only the small spectrum of electromagnetic wavelengths that we can perceive and of that spectrum we have only limited perception of (dichromaticism [color blindness] trichromaticism [normal] tetrachromaticism [four colour cones that allow greater perception of colour, recently emerged evolutionary trait]).